A conventional shape measuring instrument utilizing a non-contact sensor includes a shape measuring device which utilizes a non-contact sensor to measure a shape of a surface of an object and outputs measurement data of the shape, a computer main body which processes the measurement data outputted from the shape measuring device, and a display device which is controlled by the computer main body to display an image of the object.
FIG. 8 is a schematic diagram of an optical system of the shape measuring device. An object to be measured is irradiated with outgoing light emitted from a laser diode 111 via a beam expander 112, a first mirror 113, a second mirror 114, and a third mirror 115. Returning light reflected by a surface of the object to be measured enters a CCD line sensor portion 118 which is a non-contact sensor via the third mirror 115, the second mirror 114, a fourth mirror 116, and an imaging lens portion 117. Incidentally, the shape measuring device can scan the surface of the object to be measured by rotating a whole case (not shown) accommodating the optical system about X axis or translating the optical system along Y axis shown in FIG. 8 and rotating the third mirror 115 about Y axis.
FIG. 9 is a conceptual diagram showing a measurement principle of the shape measuring instrument. A surface of an object to be measured is irradiated with laser beam emitted from the laser diode 111 and returning light reflected by the surface of the object to be measured is concentrated by an imaging lens 117a of the imaging lens portion 117 to be focused on a line sensor 118a of the CCD line sensor portion 118. An image location of returning light measured by the line sensor 118a is outputted from the shape measuring device as measurement data. The computer main body utilizes a triangle measurement principle used for distance measurement to calculate a shape of the surface of the object to be measured based upon the measurement data.
In the shape measuring device, the position of the surface of the object to be measured is measured by measuring a displacement amount of the image location of returning light on the line sensor 118a of the CCD line sensor portion 118, but when the image location of the returning light is focused at a position deviated from the line sensor 118a (a position in a direction forming an angle of 90° to an extending direction of the line sensor 118a), the amount of light which can be received by the line sensor 118a lowers, which results in impossibility of measurement. The deviation of the image location of returning light is caused by deviation of an optical axis of the optical system of the shape measuring device.
When such optical axis deviation occurs, maintenance for performing position adjustment of the above-mentioned respective members configuring the optical system of the shape measuring device or the CCD line sensor portion 118 is required.
However, since the maintenance work must be performed by a skilled Operator or worker precisely, which results in such a problem that much cost and time are required for the maintenance work.